Backflow-free catheters for efficient and safe convection-enhanced delivery of therapeutics

Convection-enhanced delivery (CED) is an invasive drug delivery technique used to target specific regions of the brain for the treatment of cancer and neurodegenerative diseases while bypassing the blood-brain barrier. In order to prevent the possibility of backflow, low volumetric flow rates are applied which limit the achievable drug distribution volumes from CED. This can render CED treatment ineffective since a small convective flow produces narrow drug distribution inside the treatment region. Novel catheter designs and CED protocols are needed to improve the drug distribution inside the treatment region. This is especially important when administering toxic chemotherapeutics which could adversely affect other organs if backflow occurred and these drugs entered the circulating blood stream. In order to help elucidate the causes of backflow and to design backflow-free catheters, we have studied the impact that microfluid flow has on deformable brain phantom gels experimentally as well as numerically. We found that fluid injections into porous media have considerable effects on local transport properties such as porosity and hydraulic conductivity. These phenomena not only alter the bulk flow velocity distribution of the microfluid flow due to the changing porosity, but significantly modify flow direction and even volumetric flow distribution due to induced local hydraulic conductivity anisotropy. These studies led us to the development of novel backflow-free catheters with safe volumetric flow rates up to 10 µL/min. The catheter designs, numerical simulations and experimental results are described throughout this article.